I'm trying to make sense out of two articles about the effect of artificial light at night on breast cancer rates. My friend C sent me a recent piece about this from the Chronicle of Higher Education; I'll post the article as a Comment. A better piece was in
Science News. In short, the researchers say that in order to reduce your risk of breast and possibly prostate cancer:
-Sleep in a dark room and at night. More than nine hours is better than less.
-Stay away from foods with linoleic acid--which is rife in processed foods that contain corn syrup, corn oil, safflower oil and cottonseed oil. Linoleic acid helps tumors grow.
-Don't work the night shift. And if you do, don't raid the vending machines with your workmates because a lot of the packaged food in there is laden with linoleic.
Except. It's not that simple.
But first, the main idea: "'Breast tumors are awake during the day, and melatonin puts them to sleep at night," according to researcher David E. Blask, quoted in Science News. Another scientist says that you don't have to be asleep for optimum melatonin production, but you have to be in a dark room. From Science News: "Melatonin forms in the pineal gland, located in the brain, and circulates in the bloodstream. Blood concentrations of the hormone rise after dark from low daytime values and usually peak in the middle of the night." Studies have shown that women who work at night are more likely to have breast cancer, hypothetically because their melatonin levels are suppressed by light at night. In addition, a Finnish study showed that women who slept more than 9 hours a night were less likely to get breast cancer. And blind women have been shown to have less breast cancer than other women, and a "high average" level of melatonin.
Melatonin also keeps cancer cells from absorbing linoleic acid, which promotes cancer growth.
So, the experts say to sleep in a dark room. Blask does this himself and also takes melatonin supplements. Another researcher cautions people about taking melatonin because it's not regulated. But as a letter writer to Science News asked: "Are you really going to tell me you aren't going to take melatonin--if you're convinced that it might lower your chances of getting cancer by as much as 50 percent--because you are afraid of impurities?"
It seems that you could trade day for night, and get your melatonin from a dark room at midday. But that's difficult. "In theory, shift workers could swap their schedules completely and maintain a natural cycle of melatonin production during their sleep hours in the day, rather than the night," the Chronicle says, paraphrasing researcher Richard G. Stevens. "But most people who work during the night revert to a more typical schedule on their days off." Stevens tells Science News pretty much the same thing. Again, a paraphrase: "On their days off, most shift workers concentrate their activities during daylight, which upsets their circadian rhythms as much as commuting across several time zones would, he says." Does this disruption affect melatonin production? Apparently. But how? Nobody says.
And what if you sleep partly in the daytime but while wearing a blindfold, as some of our best Cancer Bitches do?
Scientists have been telling us lately that we're not getting enough
Vitamin D because we've become so afraid of the sun. Now we're not getting enough dark. Again, a letter-writer asks a good question: "If the daily light-dark cycle affects melatonin, is there a seasonal change in cancer rates in the Northern (and Southern) Hemispheres?" I have my own question: Is there more cancer in the tropics?
